In an elevator installation installed in a shaft, the shaft usually consists of solid building materials, but it can also be, at least partly, open. The elevator installation substantially consists of a car for transport of persons and/or goods. The car is connected with a counterweight by way of support means. The car is moved along a substantially vertical car travel path by means of a drive, which selectably acts on the support means or directly on the car or the counterweight, and is kept at a stop or is braked from a travel state to a stopped state by means of a brake.
Use is usually made of a brake, which is arranged at the drive, for holding and braking in the operational state and use is made of a safety brake device, which is arranged at the car, for holding and braking in the emergency case. The operational state comprises, for example, the normal operating sequences such as waiting at a floor or at a stop, receiving or unloading goods, travel of the car to another floor, stopping of the car or activities for performance of service operations on the elevator installation. By contrast, the emergency case comprises, for example, incorrect behavior during operation such as, for example, overloading of the car, failure of components, such as severing of a support means, or defects in control or mechanics.
In more recent solutions for holding and braking propose use is made of braking equipment which is frequently arranged at the car and which in the case of need comes into engagement and comprehends both states, i.e. both the operational state and the emergency situation.
Braking equipment of that kind is known from European patent document EP 0 648 703. Braking equipment mounted at the car is controlled in the drive appropriately to need and can fulfil demands resulting from the operational state and the emergency case. This braking equipment has the characteristic that in the case of wear of a brake plate a clearance changes. This has the effect that the time to bring the braking equipment into braking action changes, usually increases, since a greater advance path has to be covered, or wear-resistant brake plates have to be used. There are, for example, ceramic brake materials, which are specifically wear-resistant. Materials of that kind are, however, very expensive. Wear results from abrasion of brake material during braking.
Braking equipment which can compensate for wear of brake plates is described in U.S. Patent Application Publication No. 2006/180406. The wear compensation illustrated there can set a total sum of clearances or it can set a braking force independently of the wear of brake plates. This braking equipment also obliges the total sum of clearances to be selected to be large in such a manner that the wear of individual brake plates does not have a negative effect. This equally has the effect that the time to bring the braking equipment into braking action is correspondingly increased or that appropriately wear-resistant brake plates have to be used.